Image formation & Radiographic Quality

• device that recieves the radiaiton leaving the patient

  image receptor
• What affects the interaction with the x-ray beam ?

  quantity and quality
• What are some characteristics that determine anatomic absorption characteristics ?

  part thickness, atomic number, tissue density/compactness of cellular structures
• a process whereby some of the x-ray beam is absorbed in the tissue and some passes through the anatomic part

  differential absorption
• What abosrobs more x-ray photons than air ?

  bone
• What are the 3 process that occur to crearte image by differential absorption ?

  beam attenuation , absorption , transmission
• reduction in energy or number of primary x-ray beam as it passes throught anatomic tissue

  attenuation
• When photons interacts with anatomic tissue sturction what is the process called ?

  attenuation
• What are the two distinct process occuring during beam attenuation ?

  absorption and scattering
• ejected electron

  photoelectron
• ability to eject an electron

  ionization
• interaction of ejection

  photoelectric effect
• When ioniized atom creates a vacancy in the inner shellk the electrons from the outer shell to fill the vacancy , creates a binding energy of shells , secondary x-ray photon is emitted . What is occuring ?

  photoelectric effect
• What is the probability of total photon absorption by effect depends on :

  energy of incoming x-ray photon

  atomic number of anatomic tissue
• some incoming photons not absorbed but lose energy during interactions with atoms comprising tissue

  scattering
• What can scattering cause ?

  a compton effect or coherent scattering
• loss of energy of incoming photon with it ejects an outer-shell electron from the atom . The reamaing lower-energy x-ray photon changes direction and may leave anatomic part

  compton effect
• ejected electron

  compton ( secondary ) electron
• interaction between x-rays and matter

  compton effect
• Which type of scatter does photons interacts with outer shell electron ; outer shell electron ejected ( Compton electron ) ; ejected ( Compton) electron leaves atom with excess energy from photon ?

  compton effect
• HIgher kVp - decrease in x-ray interactions with matter
• higher kvp = increase in compton interaction opportunity
• interaction that occurs with low energy x-rays , typically below diagnostic range incoming photon interacts with atom , causing it to become excited . X-ray does not lose enrgy but changes direction

  cohrerent ( classical ) scattering
• Thickness of anatomic part , tissue type by atomic number , tissue density , and energy x-ray beam ( beam quality ) effects ?

  attenuation
• Increased thickness = Increased beam attenuation
• higher atomic number ( bone ) = more beam attenuation
• lower atomic number ( fat )= less beam attenuation
• absorption likely to occur in tissues with higher effective atomic number than with lower
• occures when an incoming photon loses some but not all of its energy, then changes its direction

  The compton effect
• The higher the kvp the higher the chance of compton scatter
• matter per unit volume or compactness of anatomic particle scomprising part

  tissue density
• denser part ( bone/muscle ) = more beam attenuation
• less dense part ( fat/air)= leass beam attenuation
• Which substance accounting fro beam attenuation the most?

  bone
• Which substance accounts for more beam attenuation ?

  muscle
• Which substance accounts for beam attenuation less ?

  fat
• which substance accounts for beam attenuation the least ?

  air
• high-penetrating x-rays= more transmission and less interaction
• Shorter wavelength and high frequency
• Low-penetrating x-rays= less transmisison and more interaction/absorption